Most roadside mailboxes and other receptacles such as for newspapers, or the like, are normally positioned with the rear of the mailbox facing the house or other building from which it is normally observed. Thus, a signal flag, or the like, placed at the rear of the mailbox generally has its position somewhat obscured by rear of the box, particularly if the signal remains within the perimiter of the box as it changes position when the box receives mail or some other article, as in the following patents: U.S. Pat. No. 889,727, and U.S. Pat. No. 2,927,726. Both of these patents have a signal which is obscured from the rear of the box by the perimeter of the box. In the first patent the signal is a knob "a" shown on a rod "6" with an abutment plate "6a" on an opposite end of the rod and within the box, so that the signal knob is at the same general position as viewed from the rear, whether or not the knob is extended from or withdrawn toward the box. The other patent is much newer, but is otherwise similar to the first noted patent, but adds a lower signal flag "52" which depends through a slot "16" in the bottom of the receptacle. This lower signal would require provision of a slot in the bottom of the box, and therefore would not be practical for installation on pre-existing boxes. In U.S. Pat. No. 2,496,962, the objection of the signal being obscured from the rear of the box by the perimiter of the box is generally overcome, but is not suitable for use on pre-existing boxes because, again, a slot must first be provided in the bottom of the box, and a pair of ears "27" would have to be secured to the box adjacent the ends of the slot.
Other patents, which are primarily concerned with operaters or retainers for the convention flag signal on a mailbox, include: U.S. Pat. Nos. 1,316,837; 1,927,736; 3,166,241; 3,392,911; and 3,623,655. While these five patents are known to applicant, they are not felt to be partcularly pertinent to the present invention.